So there is this SELECT:
SELECT * FROM table1 WHERE txtvalue REGEXP '[0-9]+' AND CAST(txtvalue
AS DOUBLE) > 50;

basically first it checks if txtvalue is a number and then cast this
number to double and checks if it is grater than 50, right? So why I
get error: "Cannot cast 'blablabla' to DOUBLE' ? Shouldn't first
condition eliminate checking second condition if txtvalue isn't a
number?